Benthos 500

Now that Aquastar is firmly back in the public eye thanks to the success of the Deepstar 2020, I thought it might be fun to review some of their vintage watches. As the Benthos 500 is probably the watch that everyone wants Aquastar to reissue next, it seemed like a good place to start.

Design work on the Benthos 500 began in 1965. The name Benthos was decided on. It comes from the Greek word meaning the “bottom of the sea”. When I was researching my book on Aquastar I had access to a number of documents from the old archive and one that I discovered, contained the minutes of meeting between Frédéric Robert who was the founder of Aquastar and Marc Jasinski who was the Head of Aquastar’s Research and Development from 1963 to 1965, where they discussed what the follow up to the Deepstar should be. What is interesting from those notes is that it was decided not to continue with the Felsa 4000 movement that was used in the Regate but go with a new movement because it was considered that the 4000 was reaching end of life. In the end, the Benthos 500 was launched with a 17 jewels A. Schild 1902 (21,600 bph). This was changed to the 17 jewels, A. Schild 2162 (28,800 bhp) for the 2nd generation of the watch, but more of that later.

When the Benthos 500 hit the market the trend for making dive watches bigger had already began. The DOXA SUB 300 which was released in 1967 was considered a big watch for the time. It measured 45mm in length, 45mm wide, including the crown, 20mm lug width and 10mm high from caseback to top of bezel. The domed perspex crystal took the height to 12mm.

The 300T released a year later flattened the crystal but increased the case thickness so that the watch was now 13mm high. The Benthos 500 weighed in at 46mm lug to lug, 43mm wide (48mm if you measure across the offset crown), 16mm high, 20mm lug width and made other dive watches from the period look anorexic. It also incorporated a 60 click bezel which was large and easy to grip even with gloved fingers.

The images below show the Benthos 500 from the side.

The screwdown crown sat at the 2 o’cclock position and the Totalizer stop / start and reset actuator button was positioned at the 4 o’clock position

The image below shows the Benthos 500 and DOXA 300T side by side with the 300T at the top. With a watch head weight of 185 grams, the Benthos 500 entered the market in the heavyweight division.

The Benthos 500 was so named because it was designed to withstand the pressure at a depth of 500 meters. It has been claimed that it was the first dive watch to achieve this rating and there are good reasons to believe the claim is valid. The case used rounded o-rings rather than the flat profile ones used by all watch manufactures up until then. The design also used an unusually large crystal, measuring 4mm thick.

The caseback used the by now standard 6 slot opener rather than the 18 sided star caseback seen in the earlier Aquqstar 60 and 63.

Many people looking at a vintage Benthos 500 would be forgiven in thinking that the red, arrow shaped, hand was there because the movement incorporated a GMT function. Good guess but totally wrong. The Benthos 500 took its design queues from the Deepstar and incorporated a 60 minute Totalizer. Originally based on an A. Schild 1902, the movement was modified to to incorporate the flyback counter. The next image shows how the top plate of the Aquqstar version of the movement was modified to allow the Totalizer to be mounted.

Activated using a monopusher at the 4 o’clock position the 60 minute timer was used to time a dive in conjunction with the minute markings on the bezel. Aquastar patented the design in 1968

I mentioned earlier about how the movement changed from the A. Schild 1902 to the A. Schild 2162 and about the large bezel. Both play a part in the second generation Benthos 500.

The following table illustrates the differences

You can see that the case dimensions changed slightly, increasing in length to 47mm and shrinking in width to 42mm. The reason for this is believed to be due to feedback from divers. With the first generation case it can be clearly seen that the case is wider than the bezel. It is nicely illustrated in an early design drawing shown below. Note that the Totalizer button is shown as a crown in the drawing.

With gloved hands it is far more likely a diver will contact the case side rather than the bezel. The second generation fixed this with the case side and bezel being almost the same width, making it easier to grab the bezel at first touch.

Cosmetically, there were some changes to the lettering on the dial, such as: the Letters SA added under the Aquastar – Genève wording and the placement of the ‘T Swiss Made T’ wording around the 6 o’clock marker.

The original watches had the lettering Swiss Made T written continuous along the bottom of the dial. The second generation had them split either side of the 6 o’clock marker with an added T so it was T SWISS MADE T.

Originally the Benthos 500 was available with black or blue dials with corresponding bezel insert color but now came a variation. There was a version with the same Aquastar decompression bezel as used on the Deepstar. These are very rare and Cliff Diamond who supplied me with superb pictures for the Aquastar book has one of the best examples.

One of the problems with writing about vintage watches is trying to get exact production dates and numbers. Even though I had access to a number of old documents from the 1960s and 1970s it proved very difficult to determine when the Benthos 500 was released. I mentioned the Minutes of Meeting above which were dated from June 1965 and the Totalizer patent that was submitted in 1967. It would seem reasonable that the watch was released maybe 1966 or 1967 or even 1968 but other documents which have recently come to light, including invoices from a case manufacturer, seem to indicate that the watch may not have been released until 1970. It does seem strange that a design initiated in 1965 took 5 years to appear on the market. However, this could be verified by the fact that the Benthos 500 first appeared in the 1970 Scubapro Catalog. The image below is from that catalog and shows the first generation Benthos 500. The second generation watch didn’t appear until the 1974 catalog, making its final appearance in the 1975 catalog. By this time Scubapro had been distributing Aquastar watches for over 12 years.

The Benthos 500 is without question one of the most iconic dive watches you can own. It is also one that is rarely seen. Up until last year Aquastar was really a company you had never heard of. You might have seen the Deepstar in images from Jacques Cousteau’s The Silent World but it is unlikely you knew anyone who had one and even more unlikely anyone who had a Benthos 500.

Things have changed, and Aquastar is back and the Deepstar 2020 proved it was back with a bang. What’s next? Well, it is no surprise that watch enthusiasts are clamoring for another classic Aquastar classic design reissue like the Regate or the Benthos 500.

Unfortunately neither of these specialized movements are available today. In the case of the Benthos 500 it would take a completely new movement design which incorporated the functionality of the Totalizer or a module which could piggyback onto, say, an ETA 2824. Will it ever happen? I don’t know. What I do know is that the Benthos 500 is a fantastic piece of dive watch history and worthy of a place in any collection.